Dataset Information

Prenatal arsenic exposure and the epigenome: identifying sites of 5-methylcytosine alterations that predict functional changes in gene expression in newborn cord blood and subsequent birth outcomes.

ABSTRACT: Prenatal exposure to inorganic arsenic (iAs) is detrimental to the health of newborns and increases the risk of disease development later in life. Here we examined a subset of newborn cord blood leukocyte samples collected from subjects enrolled in the Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gómez Palacio, Mexico, who were exposed to a range of drinking water arsenic concentrations (0.456-236 µg/l). Changes in iAs-associated DNA 5-methylcytosine methylation were assessed across 424,935 CpG sites representing 18,761 genes and compared with corresponding mRNA expression levels and birth outcomes. In the context of arsenic exposure, a total of 2919 genes were identified with iAs-associated differences in DNA methylation. Site-specific analyses identified DNA methylation changes that were most predictive of gene expression levels where CpG methylation within CpG islands positioned within the first exon, the 5' untranslated region and 200 bp upstream of the transcription start site yielded the most significant association with gene expression levels. A set of 16 genes was identified with correlated iAs-associated changes in DNA methylation and mRNA expression and all were highly enriched for binding sites of the early growth response (EGR) and CCCTC-binding factor (CTCF) transcription factors. Furthermore, DNA methylation levels of 7 of these genes were associated with differences in birth outcomes including gestational age and head circumference.These data highlight the complex interplay between DNA methylation, functional changes in gene expression and health outcomes and underscore the need for functional analyses coupled to epigenetic assessments.

SUBMITTER: Rojas D

PROVIDER: S-EPMC4274382 | biostudies-other | 2015 Jan

REPOSITORIES: biostudies-other

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Prenatal arsenic exposure and the epigenome: identifying sites of 5-methylcytosine alterations that predict functional changes in gene expression in newborn cord blood and subsequent birth outcomes.

Rojas Daniel D Rager Julia E JE Smeester Lisa L Bailey Kathryn A KA Drobná Zuzana Z Rubio-Andrade Marisela M Stýblo Miroslav M García-Vargas Gonzalo G Fry Rebecca C RC

Toxicological sciences : an official journal of the Society of Toxicology 20141010 1

Prenatal exposure to inorganic arsenic (iAs) is detrimental to the health of newborns and increases the risk of disease development later in life. Here we examined a subset of newborn cord blood leukocyte samples collected from subjects enrolled in the Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gómez Palacio, Mexico, who were exposed to a range of drinking water arsenic concentrations (0.456-236 µg/l). Changes in iAs-associated DNA 5-methylcytosine methylation were assessed acr ...[more]

PMID: 25304211

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Project description:Prenatal exposure to inorganic arsenic (iAs) is detrimental to the health of newborns and increases the risk of disease development later in life. Here we examined a subset of newborn cord blood leukocyte samples collected from mothers enrolled in the Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gomez Palacio, Mexico who were exposed to a range of drinking water arsenic concentrations (0.456-236 µg/L). Changes in iAs-associated DNA 5-methyl cytosine methylation were assessed across 424,935 CpG sites representing 18,761 genes and were compared to corresponding expression levels and birth outcomes. In the context of arsenic exposure, a total of 2,705 genes were identified with iAs-associated differences in DNA methylation. Site-specific analyzes identified DNA methylation changes that were most predictive of gene expression levels. Specifically, CpG methylation within CpG islands positioned within the first exon and 200bp upstream of the transcription start site yielded the most significant association with gene expression levels. A set of 16 genes was identified with correlated iAs-associated changes in DNA methylation and mRNA expression and all were highly enriched for binding sites of the early growth response (EGR) and CCCTC-binding factor (CTCF) transcription factors. Furthermore, DNA methylation levels of seven of these genes were associated with differences in birth outcomes including gestational age, placental weight and head circumference. These data highlight the complex interplay between DNA methylation and functional changes in gene expression and health outcomes and underscore the need for functional analyzes coupled to epigenetic assessments. 48 DNA methylation profiles were obtained but only 38 samples corresponding to samples also analyzed for gene expression (see Rager 2014) were further normalized and used in the publication from the Biomarkers of Arsenic (BEAR) cohort were analyzed for DNA methylation profiles.

Project description:The Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gómez Palacio, Mexico was recently established to better understand the impacts of prenatal exposure to inorganic arsenic (iAs). In this study, we examined a subset (n = 40) of newborn cord blood samples for microRNA (miRNA) expression changes associated with in utero arsenic exposure. Levels of iAs in maternal drinking water (DW-iAs) and maternal urine were assessed. Levels of DW-iAs ranged from below detectable values to 236 µg/L (mean = 51.7 µg/L). Total arsenic in maternal urine (U-tAs) was defined as the sum of iAs and its monomethylated and dimethylated metabolites (MMAs and DMAs, respectively) and ranged from 6.2 to 319.7 µg/L (mean = 64.5 µg/L). Genome-wide miRNA expression analysis of cord blood revealed 12 miRNAs with increasing expression associated with U-tAs. Transcriptional targets of the miRNAs were computationally predicted and subsequently assessed using transcriptional profiling. Pathway analysis demonstrated that the U-tAs-associated miRNAs are involved in signaling pathways related to known health outcomes of iAs exposure including cancer and diabetes mellitus. Immune response-related mRNAs were also identified with decreased expression levels associated with U-tAs, and predicted to be mediated in part by the arsenic-responsive miRNAs. Results of this study highlight miRNAs as novel responders to prenatal arsenic exposure that may contribute to associated immune response perturbations. We assessed the impact of prenatal exposure to arsenic on genome-wide miRNA expression profiles and their potential influence on gene expression patterns in the Biomarkers of Exposure to ARsenic (BEAR) prospective pregnancy cohort. This cohort includes residents from Gómez Palacio, located in the state of Durango in the Lagunera region of Northern Mexico. A total of 200 pregnant women residing in Gómez Palacio, State of Durango, Mexico, were recruited at the General Hospital of Gómez Palacio to participate in the BEAR prospective pregnancy cohort. The present study focuses on miRNA expression profiles and utilizes 40 samples obtained from mother-newborn pairs selected from the larger cohort (n=200). The subcohort was selected to include subjects exposed to varying levels of arsenic as determined by both total arsenic in maternal urine (U-tAs) and inorganic arsenic in drinking water (DW-iAs). Cord blood samples were collected from the newborns immediately after infant delivery. Blood samples were collected using PreAnalytix PaxGene RNA tubes and extracted using the PAXgene RNA Kit, per standard protocol (Qiagen, Valencia, CA). Isolated RNA used for microarray analysis were amplified and labeled using the NuGEN Ovation Pico WTA System V2 and Encore Biotin Module, respectively (NuGEN, San Carlos, CA). RNA isolated from 40 cord blood samples were labeled and hybridized to the Agilent Human miRNA Microarray, based off miRBase v16.0.

Project description:The Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gómez Palacio, Mexico was recently established to better understand the impacts of prenatal exposure to inorganic arsenic (iAs). In this study, we examined a subset (n = 40) of newborn cord blood samples for microRNA (miRNA) expression changes associated with in utero arsenic exposure. Levels of iAs in maternal drinking water (DW-iAs) and maternal urine were assessed. Levels of DW-iAs ranged from below detectable values to 236 µg/L (mean = 51.7 µg/L). Total arsenic in maternal urine (U-tAs) was defined as the sum of iAs and its monomethylated and dimethylated metabolites (MMAs and DMAs, respectively) and ranged from 6.2 to 319.7 µg/L (mean = 64.5 µg/L). Genome-wide miRNA expression analysis of cord blood revealed 12 miRNAs with increasing expression associated with U-tAs. Transcriptional targets of the miRNAs were computationally predicted and subsequently assessed using transcriptional profiling. Pathway analysis demonstrated that the U-tAs-associated miRNAs are involved in signaling pathways related to known health outcomes of iAs exposure including cancer and diabetes mellitus. Immune response-related mRNAs were also identified with decreased expression levels associated with U-tAs, and predicted to be mediated in part by the arsenic-responsive miRNAs. Results of this study highlight miRNAs as novel responders to prenatal arsenic exposure that may contribute to associated immune response perturbations. We assessed the impact of prenatal exposure to arsenic on genome-wide miRNA expression profiles and their potential influence on gene expression patterns in the Biomarkers of Exposure to ARsenic (BEAR) prospective pregnancy cohort. This cohort includes residents from Gómez Palacio, located in the state of Durango in the Lagunera region of Northern Mexico. A total of 200 pregnant women residing in Gómez Palacio, State of Durango, Mexico, were recruited at the General Hospital of Gómez Palacio to participate in the BEAR prospective pregnancy cohort. The present study focuses on gene expression profiles and utilizes 38 samples obtained from mother-newborn pairs selected from the larger cohort (n=200). The subcohort was selected to include subjects exposed to varying levels of arsenic as determined by both total arsenic in maternal urine (U-tAs) and inorganic arsenic in drinking water (DW-iAs). Cord blood samples were collected from the newborns immediately after infant delivery. Blood samples were collected using PreAnalytix PaxGene RNA tubes and extracted using the PAXgene RNA Kit, per standard protocol (Qiagen, Valencia, CA). Isolated RNA used for microarray analysis were amplified and labeled using the NuGEN Ovation Pico WTA System V2 and Encore Biotin Module, respectively (NuGEN, San Carlos, CA). RNA isolated from 38 cord blood samples were labeled and hybridized to the Affymetrix Human Gene 2.0 ST Array.

Project description:BackgroundAn emerging body of evidence indicates that early-life arsenic (As) exposure may influence the trajectory of health outcomes later in life. However, the mechanisms underlying these observations are unknown.ObjectiveThe objective of this study was to investigate the influence of prenatal As exposure on global methylation of cord blood DNA in a study of mother/newborn pairs in Matlab, Bangladesh.DesignMaternal and cord blood DNA were available from a convenience sample of 101 mother/newborn pairs. Measures of As exposure included maternal urinary As (uAs), maternal blood As (mbAs) and cord blood As (cbAs). Several measures of global DNA methylation were assessed, including the [3H]-methyl-incorporation assay and three Pyrosequencing assays: Alu, LINE-1 and LUMA.ResultsIn the total sample, increasing quartiles of maternal uAs were associated with an increase in covariate-adjusted means of newborn global DNA methylation as measured by the [3H]-methyl-incorporation assay (quartile 1 (Q1) and Q2 vs. Q4; p = 0.06 and 0.04, respectively). Sex-specific linear regression analyses, while not reaching significance level of 0.05, indicated that the associations between As exposures and Alu, LINE-1 and LUMA were positive among male newborns (N = 58) but negative among female newborns (N = 43); tests for sex differences were borderline significant for the association of cbAs and mbAs with Alu (p = 0.05 and 0.09, respectively) and for the association between maternal uAs and LINE-1 (p = 0.07). Sex-specific correlations between maternal urinary creatinine and newborn methyl-incorporation, Alu and LINE-1 were also evident (p<0.05).ConclusionsThese results suggest that prenatal As exposure is associated with global DNA methylation in cord blood DNA, possibly in a sex-specific manner. Arsenic-induced epigenetic modifications in utero may potentially influence disease outcomes later in life. Additional studies are needed to confirm these findings and to examine the persistence of DNA methylation marks over time.

Dataset Information

Prenatal arsenic exposure and the epigenome: identifying sites of 5-methylcytosine alterations that predict functional changes in gene expression in newborn cord blood and subsequent birth outcomes.

Publications

Prenatal arsenic exposure and the epigenome: identifying sites of 5-methylcytosine alterations that predict functional changes in gene expression in newborn cord blood and subsequent birth outcomes.

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